research article effects of low volume fraction of...

Research ArticleEffects of Low Volume Fraction of Polyvinyl AlcoholFibers on the Mechanical Properties of Oil Palm ShellLightweight Concrete

Ming Kun Yew,1 Hilmi Bin Mahmud,1 Bee Chin Ang,2 and Ming Chian Yew1

1Department of Civil Engineering, Faculty of Engineering, University of Malaya, Lembah Pantai, 50603 Kuala Lumpur, Malaysia2Center of Advanced Materials, Department of Mechanical Engineering, Faculty of Engineering,University of Malaya, 50603 Kuala Lumpur, Malaysia

Correspondence should be addressed to Ming Kun Yew; [email protected]

Received 9 August 2014; Revised 24 November 2014; Accepted 24 November 2014

Academic Editor: Hao Wang

Copyright © 2015 Ming Kun Yew et al.This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

This paper presents the effects of low volume fraction (𝑉𝑓) of polyvinyl alcohol (PVA) fibers on the mechanical properties of oilpalm shell (OPS) high strength lightweight concrete mixtures. The slump, density, compressive strength, splitting tensile strength,flexural strength, andmodulus of elasticity under various curing conditions have beenmeasured and evaluated.The results indicatethat an increase in PVA fibers decreases the workability of the concrete and decreases the density slightly. The 28-day compressivestrength of oil palm shell fiber-reinforced concrete (OPSFRC) high strength lightweight concrete (HSLWC) subject to continuousmoist curing was within the range of 43–49MPa. The average modulus of elasticity (𝐸) value is found to be 16.1 GPa for all mixes,which is higher than that reported in previous studies and is within the range of normal weight concrete. Hence, the findings ofthis study revealed that the PVA fibers can be used as an alternative material to enhance the properties of OPS HSLWC for buildingand construction applications.

1. Introduction

Concrete is the most widely used construction material incivil engineering projects worldwide. Huge quantities of dif-ferent types of concrete have been produced annually. Fromthe various kinds of concrete, lightweight concrete (LWC)is one of the most interesting subjects for researchers. LWCis used extensively by the building construction industryas nonstructural wall panels, partitions, light tiles, bricks,and architectural exterior finishing. Since their mechanicalproperties are considerably lower than those for normalweight concrete, the structural use of LWC is limited asload-bearing structural members. In order to use LWC forstructural purposes, the material must be engineered to pro-vide adequate strength, ductility, or a combination of both.Hence, the amount of lightweight aggregate concrete (LWAC)is increasing, and research and development are ongoingworldwide to develop new techniques and materials as well

as investigating the engineering properties of such materials.Recently, a high strength lightweight aggregate concrete(HSLWAC) achieved a compressive strength in the range of40–100MPa by using several types of LWAs [1–4]. However,an increase in concrete strength results in brittleness of theconcrete during compression and tension [5–7], specificallyin the case of LWAC [6]. By advancement in fiber-reinforcedcementitious composites, lightweight cement compositesreinforced with a small amount of discontinuous (steel,polypropylene, and nylon) fibers may prove themselves asfavourable construction materials. However, the main disad-vantage of adding steel fibers into OPSLWC in a fresh state isits significant reduction in slump value and increased density[8]. Chen and Liu [7] have intensively studied the effect byusing 1% of volume content of polypropylene fibers (length:15mm, aspect ratio: 150) on LWC. Based on their findings,the addition of polypropylene fibers into LWCmixtures usingexpanded clay resulted in a reduction of slump values of

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2015, Article ID 425236, 11 pageshttp://dx.doi.org/10.1155/2015/425236

2 Advances in Materials Science and Engineering

about 20.8%. Furthermore, the addition of polypropylene andnylon insignificantly increased the mechanical properties ofOPS concrete, particularly for the tensile strength [9]. A newmethod that can be adopted to resolve the brittle texture ofLWAC is to combine the PVA fibers with heat-treated OPSconcrete to enhance its mechanical properties.

Themost popular method of LWC production is throughthe use of LWAs [10], which may be either natural ormanufactured. The LWA can be natural aggregates such aspumice, scoria, and those of volcanic origin whereas artificialaggregates include expanded blast-furnace slag, vermiculite,and clinker aggregates [11]. Another type of natural LWA isagricultural resource OPS. It has known that there are largeamounts of agricultural residue in countries where the oilpalm industry is dominant such as Malaysia, Indonesia, andNigeria.Malaysia is one of theworld leaders in the productionand export of palm oil [12]. The production of OPS hasestimated that over 4 million tonnes are produced annuallyin this country alone [13]. The densities of OPS are withinthe range of most typical structural LWAs [14–16]. StructuralLWC is typically defined as concrete with an oven-dry densityless than 2000 kg/m3 [17, 18].The 28-day oven-dry density forthe crushedOPSmixes range between 1871–1876 kg/m3 [4]. Ithas reported that the mechanical properties of OPS concreteare lower than other types of LWAC [10]. Recently, Yew et al.[4] reported that the different species and age categories ofOPS coarse aggregates show the most significant impact onthe performance of HSLWC compared to previous studies.

Most of the research on OPS lightweight concrete hasfocused on the investigation of their engineering properties asthere is inadequate information concerning the enhancementof its low mechanical properties. Despite there have manyadvantages of incorporating steel fibers into OPS LWC.However, steel fibers pose several drawbacks; in particular,theworkability of fresh concrete is reduced, and the dead loadof the composite is increased [8]. To the authors’ knowledge,no studies have been conducted regarding the properties ofOPS concrete that incorporate PVA fibers. Therefore, thisstudy focuses on investigating the effects of various low𝑉𝑓 ofpolyvinyl alcohol (PVA) fibers on the mechanical propertiesof LWAC subject to different curing conditions.

2. Materials and Methods

2.1. Materials

2.1.1. Cement. The cement used in this study is ASTMtype I ordinary Portland cement (OPC) [19] with a specificgravity of 3.14 g/cm3. The Blaine’s specific surface area forthis cement is 3510 cm2/g. The chemical compositions andphysical properties of OPC are tabulated in Table 1.

2.1.2. Water and Superplasticizer (SP). Potable water is usedfor all mixes. The SP used in this study is polycarboxylicether (PCE) supplied by BASF, which complies with ASTMC494/C494M-13. The amount of SP for all mixes is keptconstant, with a value 1.5% of cement weight in order tofacilitate workability of the concrete.

Table 1: Chemical composition and physical properties of OPC.

Chemical composition (%)SiO2 21.28Fe2O3 3.36CaO 64.64MgO 2.06Al2O3 5.60SO3 2.14

Physical propertiesLOI 0.64Specific gravity 3.14Blain specific surface area (cm2/g) 3510

(a) (b)

Figure 1: Original dura (a) and tenera (b) OPS aggregates.

2.1.3. Aggregates. Local mining sand is used as fine aggre-gates, having a specific gravity, fineness modulus, waterabsorption, and maximum grain size of 2.67 g/cm3, 2.71,0.95%, and 4.75mm, respectively.

Figure 1 shows the different species of original dura andtenera OPS waste from a local crude palm oil producingmill. In this study, the OPS aggregates used are dura species.The original dura OPS was washed and sieved using a12.5mm sieve. The OPS aggregates retained in the sieve werecollected and then crushed using a stone-crushing machinein the laboratory as shown in Figure 2. The crushed OPSaggregates were sieved using a 9.5mm sieve to remove OPSaggregates with sizes greater than 9.5mm (Figure 3). It hasben reported that the maximum size of OPS changes fromoriginal (12.5mm) to crushed (9.5mm). The broken edgesof dura OPS are rough and spiky improved the physicalbond between the aggregates and hydrated cement paste andyields higher compressive strength [4]. Furthermore, theOPSaggregates were heat treated at 60∘C over a period of 0.5 husing a temperature-controlled laboratory oven. Once cooledto room temperature, they were weighed under dry roomconditions and immersed in water for 24 h. Yew et al. [20]found thatOPS aggregates were subjected to heat treatment at

Advances in Materials Science and Engineering 3

Figure 2: Stone-crushing machine for OPS aggregates.

this temperature setting and duration of the period improvedthe performance of OPS properties without compromisingthe strength of the OPSC. Due to the high water absorptionof OPS, it was subsequently air dried in the laboratory toattain a saturated surface dry (SSD) condition before mixing.The difference in quality of the crushed OPS surface betweenheat treatment and without heat treatment condition wasreported by Yew et al. [20] and shown in Figure 4. Thephysical properties of the OPS used are shown in Table 2.

2.1.4. Fibers. A photograph of the polyvinyl alcohol (PVA)fibers is shown in Figure 5 and their physical properties arelisted in Table 3.

2.2. Mix Proportions. Themix proportions used in this studyhave been shown in Table 4. The amount of volume fraction(𝑉𝑓) of fibers added to the concrete mix typically rangesbetween 0.1 and 3.0% [21]. However, fibers with an extremelyhigh 𝑉𝑓 tend to “ball” in the mix and create workabilityproblems. Hence, a low volume fraction (≤0.5%) for the PVAfibers is used in this study.The volume fractions of PVA fibersin the OPS concrete are 0, 0.125, 0.25, 0.375, and 0.5%. Thedosages of water and superplasticizer are kept constant for allmixes.

2.3. Test Methods and Curing Regimes. The procedureadopted for mixing the fiber-reinforced concrete involvesthe following steps. The sand and OPS are first poured intoa concrete mixer and dry mixed for 1min. Following this,the cement is spread and dry mixed for 1min, after whichthe specified amount of fibers is distributed and mixed for3min in the mix. This is followed by the addition of waterand superplasticizer with a mixing time of 5min. Slump testis carried out on the mixture prior to sample casting. Theconcrete specimens are cast onto oiled moulds and a pokervibrator is used to eliminate the amount of air bubbles inthe mix. For each mixture, 18 cubes (100 × 100 × 100mm)

Table 2: Physical properties of crushed-heat treatment dura OPSaggregates.

Physical property OPS OPS∗

Maximum size (mm) 9.5 9.5Specific gravity (saturated surface dry) 1.35 1.31Compacted bulk density (kg/m3) 632 628Water absorption (24 h) (%) 23.8 21.0Aggregate impact value (%) 2.38 2.36∗Dried OPS.

Table 3: Physical properties of polyvinyl alcohol fibers.

Parameter Polyvinyl alcoholLength 30mmFilament diameter 660 micronsSpecific gravity 1.3Tensile strength 800MPaFlexural strength 23GPaMelting point 225∘CColour YellowWater absorption <1% by weightAlkali resistance Excellent

Table 4: Mix proportions (kg/m3).

Mix code Cement Water Sand OPS Fiber volume(%)

V0 530 155 920 340 0V0.125 530 155 920 340 0.125V0.250 530 155 920 340 0.250V0.375 530 155 920 340 0.375V0.500 530 155 920 340 0.500

are used to determine the compressive strength at 1, 3, 7, 28,and 90 days. In addition, two cylinders (diameter: 150mm,height: 300mm), three cylinders (diameter: 100mm, height:200mm), and three prisms (100mm× 100mm× 500mm) areused to determine the modulus of elasticity, indirect tensilestrength, and flexural strength, respectively, on the 28th day.The specimens are demoulded approximately 24 hours aftercasting.

The specimens are cured under three types of curingconditions in order to determine the effects of curing envi-ronment on the 28-day compressive strength ofOPS concrete,as listed below.

CC: the specimens are cured in water at 23±3∘C until thetime of testing.

14C: the specimens are cured in water for 13 days afterdemoulding and then being air-cured in laboratory environ-ment with a relative humidity (RH %) of 60 ± 15 and atemperature of 28 ± 3∘C.


(a) (b)

Figure 3: Crushed dura (a) and tenera (b) OPS coarse aggregates.

(a)

(b)

Figure 4: Images (left) and microscopic images (right) of crushed OPS aggregates: (a) with heat treatment and (b) without heat treatment.

Figure 5: Photograph of polyvinyl alcohol fibers.

AC: the specimens are stored under laboratory environ-ment after demoulding.

3. Results and Discussion

3.1. Workability and Slump of Fiber-Reinforced Concrete.Slump tests are carried out to determine the consistency offresh concrete. The use of fibers is well known to influencethe workability and flow ability of plain concrete intrinsically[21, 22]. The slump of fresh OPS concrete decreases due to anincrease in volume fraction of the PVA fibers. The quantityof water and SP is kept constant for all mixes in this study.The addition of fibers into the mixtures from 0 to 0.125, 0.25,0.375, and 0.5% decreases the workability by 5.0, 7.5, 22.5,and 40.0%, respectively. Noushini et al. [23] reported that theaddition of monofilament PVA fibers into the mixtures from0 to 0.5% reduced the slump at about 20%. Figure 6 shows thatthere is a linear relationship between the PVA fiber volumefraction and slump for OPS concrete.


50

100

150

200

250

0.000 0.125 0.250 0.375 0.500

Slum

p (m

m)

y = −19.50x + 228.50

R2 = 0.89

Vf of PVA fibre (%)

Figure 6: Relationship between PVA fiber volume fraction andslump.

The declining trend in slump value is attributed to thefact that the addition of fibers creates a network structure inthe concrete, which restraints the mixture from segregationand flow. It can be ascertained that the fibers will absorbmore of the cement paste in order to “wrap around.” Thisphenomenon is due to the high content and large surfacearea of the fibers, and an increase in viscosity of the mixturepromotes a decrease in slump [24]. However, a number ofstudies have attempted to overcome the segregation problemby adding superplasticizers and using optimum proportionsof aggregates and sand into the concrete mixtures to achievehigh workability and flow ability [25–28]. Campione et al.[29] reported that good workability has been achieved forpumice and expanded clay LWAC reinforced with steel fibersby adding 1.5% superplasticizer of the cement weight. Ingeneral, the use of a low dosage of fibers is recommended toensure good workability for fiber-reinforced concrete [30].

3.2. Hardened Density. Steel fibers are the most commonlyused fibers for improving themechanical properties of LWACamongst the various types of fibers [31]. The relationshipbetween steel fiber volume fraction and density of Shafighet al. [8] shows that the density increases with an increasein fiber volume fraction. However, the low specific gravityof PVA fibers provides a lower density fiber-reinforced LWCwith higher strength.

Three types of densities, namely, demoulded density, 28-day air-dry density, and oven-dry density, are measuredfor all mixes. The density of the concrete mixes decreasesslightly with an increase in fiber volume fraction, which isattributed to the low specific gravity of the PVA fibers [32].The 28-day air-dry density of the V0.5 mix is found to beapproximately 1939 kg/m3, which indicates that the densityfalls within the range of those for structural lightweightconcrete even though the volume fraction of PVA fibers isonly 0.5%. The relationship between the demoulded, air-dryand oven-dry densities with respect to the volume fraction ofPVA fibers is illustrated in Figure 7. The 28-days air-dry andoven-dry densities range from 1939 to 1970 kg/m3 and 1914to 1941 kg/m3, respectively, for various volume fractions. It isfound that increasing the volume fraction from 0 to 0.125,0.25, 0.375, and 0.5% decreases the demoulded density, airdry density, and oven-dry density slightly by 0.2, 0.6, 1.0, and

1900

1920

1940

1960

1980

2000

2020

0 0.125 0.250 0.375 0.500

DemouldedAir dryOvendry

Vf of PVA fibre (%)

y = −7x + 2009

R2 = 0.99

y = −7.9x + 1978.9

R2 = 0.98

y = −6.7x + 1948.5

R2 = 0.99

Den

sity

(kg/

m3)

Figure 7: Relationship between PVA fiber volume fraction anddensities.

1.3% at 1-day age, 0.4, 0.6, 1.2, and 1.6% at 28-days age and0.3, 0.6, 1.0, and 1.4% at 28-days age, respectively. Althoughthe addition of the very low specific gravity PVA into heat-treated OPS concrete produced an insignificant change indensity. However, their contribution to the density cannot beignored. Itmight be attributed to PVA tend to displacemortarin concrete as the diameter of PVA is 0.66mm. Furthermore,it has been reported that there is a marginal reduction indensity without alterations in mechanical properties whenpolypropylene (PP) fibers are added into OPSFRC [9, 33].Hence, there is substantial cost savings by providing less deadload for LWC in this study.

3.3. Compressive Strength

3.3.1. Continuous Moist Curing. The effects of PP fibers (𝐿 =15mm and 𝐷 = 0.10mm) on the properties of LWAC havebeen much researched amongst the various types of fibers.It has been reported that PP fibers result in a decrease incompressive strength of LWAC [24]. It can be seen that thecompressive strength of concrete increases for all ages withan increase in PVAfiber volume fraction (Table 5). Increasingthe PVAfiber volume fraction from0 to 0.125, 0.25, 0.375, and0.50% increases the compressive strength by roughly 0.9, 6.2,8.7, and 13.1% at 28-days age and 0.6, 8.0, 10.0, and 18.9% at 90-days age, respectively. Comparison between the compressivestrength of the fiber-reinforced concrete during the formerand latter ages indicates that the rate of compressive strengthdevelopment increases from the former to latter ages and isparticularlymore pronounced for concretemixes with higherPVA fiber content. This trend can be clearly observed fromthe percentages of the 28-day compressive strength (shownwithin the parentheses) for each age in Table 5. It can be seenthat the percentage of compressive strength at 3 days and 7days decreases with an increase in PVA fiber volume fractionwhereas the value increases at 90-day age. This trend isattributed to the higher rate of compressive strength gained at


Table 5: Development of compressive strength of lightweight OPS FRC under continuous moist curing.

Mix code Compressive strength (MPa)a

1 d 3 d 7 d 28 d 90 d

V0 29.32 (68%) 33.04 (77%) 39.48 (92%) 42.89 43.29 (101%)(0.61) (0.33) (0.48) (0.49) (0.67)

V0.125 28.81 (67%) 32.61 (75%) 39.70 (91%) 43.29 43.54 (101%)(0.83) (0.97) (0.62) (0.73) (0.89)

V0.250 28.95 (64%) 34.60 (76%) 39.92 (88%) 45.56 46.77 (103%)(0.90) (0.97) (0.81) (0.86) (0.78)

V0.375 29.65 (64%) 35.88 (77%) 41.95 (90%) 46.62 47.60 (102%)(0.83) (0.95) (0.75) (0.87) (0.95)

V0.500 30.66 (63%) 37.58 (77%) 43.75 (90%) 48.51 51.48 (106%)(0.88) (0.80) (0.81) (1.22) (0.66)

aThe data in parentheses are percentages of 28-day compressive strength.Note: the standard deviations (in MPa) of the corresponding mechanical properties are shown in the bracket (below).

latter ages, and the rate is particularly significant for the 0.5%PVA fiber volume fraction. The relative strength between thecontrol and PVA fiber volume fraction from 0 to 0.125, 0.25,0.375, and 0.50% increases the compressive strength at about0.9, 0.6, 2.7, 2.1, and 6.1% at 90-day age as compared to 28-dayage. It is apparent that PVA fiber volume fraction up to 0.25%,the performance of PVA fibers in the OPS concrete increasesat latter ages, which is possibly due to the improvement ofPVA fiber-mortar interfaces [34].

Shafigh et al. [8] have shown the possibility of producinggrade 40 strength OPS concrete at the age of 28 days.Based on the findings of this study, it can be deducedthat the production of grade 40 OPS concrete with lowercement content is possible [35], even with a low volumefraction of PVAfibers, relative to previous studies. In practicalapplications of concrete, the early-age compressive strengthtest can be used in replacement of the 28 days or other latterages for the purpose of routine quality control. In this study,two equations are generated to predict the performance ofthe concrete in latter ages. By using new (1) at the early agecompressive strength test, changes in concrete properties canbe detected at an early stage and the appropriate correctiveactions can be taken to improve concrete quality [36]:

𝐹28 = 1.35𝐹7 − 9.94,

𝐹90 = 1.40𝐹28 − 16.9.(1)

3.3.2. Effect of Curing Condition. Figure 8 illustrates the 28-days compressive strength of specimens subject to threecuring conditions, namely, continuous curing (CC), 14-days moist curing (14C) and no curing in the laboratoryenvironment (AC). It can be seen that the order of strength forthe concrete is CC> 14C>AC.The loss in 28-day compressivestrength of the specimens consisting of 0, 0.125, 0.25, 0.375,and 0.5% PVA fiber volume fraction is 14.9, 14.7, 13.7, 10.8, and9.6%, respectively, under AC curing. The values decrease to5.4, 6.4, 6.8, 8.3, and 5.4%, respectively, when the specimensare cured over a short period (14C).

The results show that the behaviour of OPS concretecontaining PVA fibers up to 0.5% by volume under nocuring

34.00

36.00

38.00

40.00

42.00

44.00

46.00

48.00

50.00

0 0.125 0.250 0.375 0.500

Com

pres

sive s

treng

th at

28

days

(MPa

)

CC14 CAC

Vf of PVA fibre (%)

y = 1.457x + 41.003

R2 = 0.97y = 1.285x + 38.589

R2 = 0.86

y = 1.942x + 33.81

R2 = 0.97

Figure 8: Relationship between PVA fiber volume fraction andcompressive strength under different curing conditions on the 28thday.

regimes is almost similar to that of OPS concrete underCC condition. However, OPS concrete with a PVA fibervolume fraction exceeding 0.375% exhibits lower strengthloss under AC curing as compared to CC and 14C. Thisobservation shows that although the strength ofOPS concreteappears to be sensitive to poor curing [8], the sensitivity ofcompressive strength loss decreases by incorporating PVAfibers with a volume fraction exceeding 0.375%. This is dueto the possibility that when the PVA fiber content is high(particularly a volume fraction of 0.5%), the fibers arrestthe development and number of original shrinkage cracks.Therefore, it can be deduced PVA fibers offer an additionalbenefit, whereby the sensitivity of OPS concrete is reducedunder poor curing environments. Furthermore, it can beobserved from Figure 7 that the 28-day compressive strengthof OPS concrete increases linearly with an increase in PVA


0

5

10

15

20

25

30

35

0 0.002 0.004 0.006 0.008

Stre

ss (M

Pa)

Strain (mm/mm)

V0V0.125V0.25

V0.375V0.5

Figure 9: Typical stress-strain relationship.

fibers volume fraction. A prominent feature of this figure isthat the slope of the straight line for AC specimens is thesteepest (slope = 1.942), whereas the slope for CC and 14Cspecimens is nearly equal with a value of 1.457 and 1.285,respectively. This shows the positive effect of incorporatingPVA fibers into OPS concrete even in poor curing conditions.

3.3.3. Strain at Peak Stress. Figure 9 shows the stress-straincurves of sample at 28-day continuously moist curing for V0,V0.125, V0.25, V0.375, and V0.5 mixes under compression.The stress-strain curves of most LWACs for both normal andhigh strength levels are typically linear to levels approaching90% or higher of the failure strength [31, 37, 38]. It is usually30 to 45% for a normal weight concrete (NWC) [31]. Thisshows that LWACs aremore brittle thanNWCs, which causesits explosive fracture after peak load [39]. One of the disad-vantages that prevented its use in concrete structures is dueto the brittle nature of LWC. Therefore, the possible solutionis to use PVA fibers to enhance the brittleness of LWC.

From the results, the strain at peak stress (𝜀) of the V0,V0.125, V0.25, V0.375, andV0.5mixesmeasured in this studyvaries from 0.0029 to 0.0045. The 𝜀 value of the V0 andV0.125 mixes is of similar value of approximately 0.0030.However, when the inclusion of PVA fiber is up to 0.25–0.5%, the 𝜀 value increased about 41, 52, and 55%, which issignificant. It could be noted that the PVA fiber up to 0.25%reinforced OPSLWA shows different behavior to plain OPSC.This phenomenon might be attributed to arresting of cracksby PVA fibers which contribute to very large deformationsbefore total uncontrollable collapse. It has been shown that,in contrast to many types of structural lightweight aggregateconcretes, plain OPS concrete is a ductile material [40]. Inaddition, it was found that the addition of steel fiber intoOPS concrete increases the strain capacity and improves itsductility performance [8]. However, themain disadvantage ofadding steel fibers into OPSLWC is its significant incrementin density compared with PVA fibers. Such improvement inthe ductility performance of OPS concrete can be observed in

OPS concrete containing PVA. It is clear that by adding PVAto the OPS concrete the strain of the concrete correspondingto the peak stress increases significantly. Increasing in thestrain capacity of concrete results in an increase in the area ofthe stress-strain diagram and energy absorption capacity andalso changed the concrete into a more ductile material. Thestress-strain relationship for uniaxial compression of OPSCand PVA fiber-reinforced OPSC is shown in Figure 9. It hasbeen reported that the improvement in resistance to crackingdue to restrained shrinkage is of the advantages of greaterstrain capacity of a concrete [41]. Furthermore, it should benoted that the 𝜀 value of NWC with normal strength is in therange of 0.0015 to 0.002 [42]. Shafigh et al. had shown thatwhen 0.5 and 1% volume fraction of the steel fiber is addedto an OPS concrete, its 𝜀 value increases about 20 and 35%,respectively [8].

3.4. Splitting Tensile Strength. Fiber-reinforced concrete andpolymer concrete have been developed over the years in orderto improve the tensile strength of concrete [43]. It has beenreported that the addition of fibers provides a significantincrease in splitting tensile strength of LWAC and semi-LWAC concrete [43–45]. Figure 10 shows the 28-day splittingtensile strength increases from 2.88 to 3.74MPa when thefiber content is increased from 0 to 0.5%.The rate of increasefor V0.125, V0.25, V0.375, and V0.5 mixes is determined tobe 9.4, 11.1, 19.8, and 29.9%, respectively, which indicates aconsiderable improvement in the splitting tensile strength ofthe OPS concrete, even in the presence of low fiber content.

It has also been reported that the 28-days splitting tensilestrength of OPS concrete under moist curing is within therange of 1.9–2.41MPa [46, 47], which is approximately 6–10%of the corresponding cube compressive strength. Chen andLiu [24] investigated the effect of three types of fibers on theproperties of expanded clay HSLWAC, in which the amountof each type of fibers is 1%.They reported that PP fibers resultin a slight reduction in splitting tensile strength of about 2%.In this study, the splitting tensile strength for OPS concreteis determined to be 6.7%, which falls within the range of6.7–7.7%, of the compressive strength. This shows that thePVA fibers obviously enhance the tensile to compressivestrength ratio. Figure 10 shows the relationship between thesplitting tensile strength and PVA fiber volume fraction. Itis clear that the splitting tensile strength increases with anincrease in PVA fiber content. The relationship between thetwo parameters is found to be parabolic, whereby 𝐹𝑡 =(0.0171)𝑉2𝑓 + (0.0991)𝑉𝑓+ 2.798 and the 𝑅2 value is 0.97. 𝐹𝑡and𝑉𝑓 represent the splitting tensile strength (MPa) and fibervolume fraction (%), respectively. Furthermore, Figure 11shows a parabolic correlation with a strong correlation (𝑅2 =0.97) between fiber volume (%) and the splitting tensilestrength to compressive strength.

An equation has been proposed to correlate splittingtensile strength of OPSFRC by Yap et al. [9] by incorporatingPP and nylon fibers as shown in

𝑓𝑡 = 0.52√𝑓cu, (2)


2.5

2.7

2.9

3.1

3.3

3.5

3.7

3.9

0 0.125 0.250 0.375 0.500

Split

ting

tens

ile st

reng

th at

28

days

(MPa

)

Vf of PVA fibre (%)

Figure 10: Relationship between PVA fiber volume fraction andsplitting tensile strength.

5.60

6.10

6.60

7.10

7.60

8.10

0 0.125 0.250 0.375 0.500

Split

ting

tens

ile st

reng

th to

com

pres

sive

stren

gth

ratio

(%)

Vf of PVA fibre (%)

Figure 11: Relationship between PVA fiber volume fraction and thesplitting tensile strength to compressive strength ratio.

where 𝑓𝑡 and 𝑓cu represent the splitting tensile and cubecompressive strengths in MPa, respectively.

A new equation to correlate splitting tensile strengthand compressive strength of OPSFRC is proposed in (3),whereby a higher coefficient of correlation is produced(accuracy = ±10%). An accurate prediction of tensile strengthof the concrete imperative in mitigating cracking problemsminimizes the failure of concrete in tension and increasesshear strength prediction as shown below

𝑓𝑡 = 0.49√𝑓cu. (3)

3.5. Flexural Strength. The relationship between PVA volumefraction and flexural strength is shown in Figure 12. It can beseen that the 28-day flexural strength increases from 4.17 to5.49MPa, ranging from9.7 to 11.3%of the 28-day compressivestrength when the fiber content is increased from 0 to 0.5%.This range is higher than the findings of previous studieswhich focused on OPS LWAC [46, 48] and expanded clayLWA [49].

In comparison to mix V0, the rate of increase of flexuralstrength is obtained to be 9, 26, 28, and 32% forV0.125, V0.25,V0.375, andV0.5mixes, respectively.These rates indicate that

3.50

4.00

4.50

5.00

5.50

6.00

0 0.125 0.250 0.375 0.500Flex

ural

stre

ngth

at 2

8 da

ys (M

Pa)

Vf of PVA fibre (%)

Figure 12: Relationship between PVA fiber volume fraction andflexural strength.

an increase in the PVA fiber volume fraction up to 0.25%exhibits a nearly similar effect on the increase in flexuralstrength (Figure 12). This phenomenon might be attributedto fiber clogging within the 0.25% volume fraction whichcauses more pores resulting in the similar effect on theincrease in flexural strength. However, a significant increasein flexural strength is attained with a higher fiber volumefraction of 0.5% as compared to OPS concrete. Shi et al. [50]discovered that the addition of a small amount of fibers doesnot influence the flexural strength of lightweight concrete;however, the ductility is significantly improved.They believedthat this may be due to the lower tensile strength of PP fibersas well as the weaker bonds between PP fibers and the cementmatrix compared to PVA fibers.

A relationship between the flexural strength and cubecompressive strength for OPS concrete has been proposed byAlengaram et al. [46], as given by the following equation:

𝑓𝑟 = 0.33√𝑓2cu. (4)

Lo et al. [49] proposed the following equation for LWACmade with expanded clay aggregates:

𝑓𝑟 = 0.69√𝑓cu. (5)

Furthermore, the equation for LWAC made with a combina-tion of expanded shale and clay aggregate, for cube strengths,ranging from 20 to 60MPa [51] is follows:

𝑓𝑟 = 0.463√𝑓2cu. (6)

A new equation has also been proposed to correlateflexural strength to compressive strength ofOPSLWAC in thisstudy. Equation (7) is suggested for OPSFRC with differentvolume fraction of PVA fibers to predict the flexural strengthwithin ±14%:

𝑓𝑟 = 0.393√𝑓2cu, (7)

where 𝑓𝑟, 𝑓𝑡, and 𝑓cu represent the flexural, splitting tensile,and cube compressive strength, respectively, with units inMPa.


Table 6: Measured and estimated flexural strength.

Mix code 28-day compressivestrength (MPa)

Measured flexuralstrength (MPa)

Estimated flexural strength (MPa)Equation (5) byAlengaram et al.

[46]

Equation (6) byLo et al. [49]

Equation (7) byCEB/FIP [51]

Equation (7) inthis study

V0 42.89 4.17 3.47 4.33 5.32 4.78V0.125 43.29 4.54 3.61 4.46 5.54 4.81V0.250 45.56 5.24 3.63 4.47 5.56 4.97V0.375 46.62 5.34 3.79 4.62 5.81 5.05V0.500 48.51 5.49 3.79 4.63 5.82 5.19

Table 6 shows the estimated flexural strength using thefour (2)–(5) as given. From the estimated flexural strengthvalues, it can be seen that (7) is generally acceptable to predictthe flexural strength of OPS concrete. It can be deduced fromthe results that the flexural strength of OPS concrete with andwithout fibers is comparable to artificial LWA with expandedshale and clay aggregates.

3.6. Modulus of Elasticity. In this study, the value of staticmodulus of elasticity (𝐸) is 15.3, 15.6, 16.3, 16.4, and 16.9GPafor mixes V0, V0.125, V0.25, V0.375, and V0.5, respectively.These values indicate that the addition of PVA to OPSconcrete has a significant effect on the (𝐸) value. Thisphenomenon might be attributed to the heat treatment onOPS enhancing the dimensional stability and surface qualityof OPS which improve the adhesion between the aggregateand the cement matrix. In addition, the MOE of OPSFRCwas found to be dependent on the fiber volume. It might bedue to the fact the addition of fibers contributed to crackbridging which enhances the MOE of OPSFRC. Yap et al.[9] reported that the combined effect of both silica fume andfibers (PP and nylon) enhanced the MOE of OPSFRC, evenhigher compared to OPSC with crushed OPS. However, inthe present study, the combined effect of both heat-treatedcrushed duraOPS and PVA fibers reduced the strain inducedunder compression loadings and eventually improved theMOE of OPSFRC significantly compared to previous studies.

In a previous study, the (𝐸) value of OPS concrete withtotal cementitious materials (cement/fly ash/silica fume) isreported to be 11 GPa, whereas the compressive strengthis approximately 38MPa [35]. The (𝐸) value of mix V0 isroughly 39% higher than this value.The use of duraOPSwithheat-treated and PVA fibers has a significant effect on thecompressive strength due to the enhanced adhesion betweenthe OPS and PVA fibers with the cement matrix. Hence, itcan be deduced that it is possible to attain a higher average(𝐸) value of 16.1 GPa for OPSFRC.

It has been reported by CEB/FIP that the (𝐸) value ofstructural lightweight concrete ranges between 10 and 24GPa[51]. Swamy and Lambert [52] reported (𝐸) values withinthe range of 15–22GPa for LWAC made with pulverized fuelash (PFA) aggregates. Mehta and Monteiro [53] reportedthat the (𝐸) value is 10 and 14GPa for 20 and 40MPa com-pressive strength LWC containing expanded clay aggregates,respectively. For normal weight concrete, the (𝐸) values range

from 14 to 41GPa [54]. Thus, it can be deduced that the (𝐸)value measured for the concrete in this study falls within therange of normal weight and artificial lightweight aggregateconcrete.

4. Conclusion

Based on the experimental results of this study, it can be foundthat the addition of PVA fibers enhanced the mechanicalproperties of concrete. The workability of fiber-reinforcedconcrete decreases by increasing the volume fraction of PVAfibers. A maximum reduction of 40% has been determinedfor OPS concrete with 0.5% PVA fiber content. Furthermore,the addition of PVAfibers with low specific gravity to theOPSmixtures reduces the density of the concrete. However, PVAfibers that contribute to the marginal reduction in densitycannot be ignored.The compressive strength of OPS concretehas increased for all ages with an increase in PVA fibers.The effect of PVA on compressive strength of lightweightconcrete has been shown more prominent at latter agesdue to better fiber/matrix interface adhesion. The 28-daycompressive strength of PVA fiber-reinforced OPS concreteis found to be within 43–49MPa. The addition of PVA fiberup to 0.375% had a positive effect on the compressive strengthloss under no curing (AC) condition. Therefore, it can bededuced that PVA fibers can be used to reduce the sensitivityof OPS concrete in poor curing environments. The inclusionof PVA fiber to OPS concrete increases the strain capacitycorresponding to peak stress, which causes OPS concreteto become more ductile. The addition of PVA fibers alsoenhances the splitting tensile and flexural strengths signifi-cantly up to 30 and 32%, respectively, compared to the controlconcrete. The inclusion of PVA fibers into OPS concretehas a significant effect on the modulus of elasticity. The (𝐸)value measured in this study is 16.1 GPa, which is highercompared to previous studies. Hence, it can be concluded thatPVA fiber-reinforced OPS LWC showed the possibility andaccepted performance for potential application in producinggreen composite concrete structures.

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper.


Acknowledgment

The authors wish to extend their greatest appreciation to theUniversity of Malaya for providing the financial support forthis work under the University of Malaya Research Grant(UMRG), Grant no. RP018/2012C.

References

[1] O. Kayali, M. N. Haque, and B. Zhu, “Some characteristics ofhigh strength fiber reinforced lightweight aggregate concrete,”Cement and Concrete Composites, vol. 25, no. 2, pp. 207–213,2003.

[2] M. H. Zhang, L. Li, and P. Paramasivam, “Flexural toughnessand impact resistance of steel-fibre-reinforced lightweight con-crete,”Magazine of Concrete Research, vol. 56, no. 5, pp. 251–262,2004.

[3] H. Costa, E. Julio, and J. Loureno, “New approach for shrinkageprediction of high-strength lightweight aggregate concrete,”Construction and Building Materials, vol. 35, pp. 84–91, 2012.

[4] M. K. Yew, H.Mahmud, B. C. Ang, andM. C. Yew, “Effects of oilpalm shell coarse aggregate species on high strength lightweightconcrete,” The Scientific World Journal, vol. 2014, Article ID387647, 12 pages, 2014.

[5] V. C. Li, “Large volume, high-performance applications of fibersin civil engineering,” Journal of Applied Polymer Science, vol. 83,no. 3, pp. 660–686, 2001.

[6] A. R. Khaloo and M. Sharifian, “Experimental investigation oflow to high-strength steel fiber reinforced lightweight concreteunder pure torsion,” Asian Journal of Civil Engineering, vol. 6,no. 6, pp. 533–547, 2005.

[7] B. Chen and J. Liu, “Contribution of hybrid fibers on theproperties of the high-strength lightweight concrete havinggood workability,” Cement and Concrete Research, vol. 35, no.5, pp. 913–917, 2005.

[8] P. Shafigh, H. Mahmud, and M. Z. Jumaat, “Effect of steelfiber on the mechanical properties of oil palm shell lightweightconcrete,” Materials and Design, vol. 32, no. 7, pp. 3926–3932,2011.

[9] S. P. Yap, U. J. Alengaram, and M. Z. Jumaat, “Enhancementof mechanical properties in polypropylene- and nylon-fibrereinforced oil palm shell concrete,”Materials & Design, vol. 49,pp. 1034–1041, 2013.

[10] R. Polat, R. Demirboga, M. B. Karakoc, and I. Turkmen, “Theinfluence of lightweight aggregate on the physico-mechanicalproperties of concrete exposed to freeze-thaw cycles,” ColdRegions Science and Technology, vol. 60, no. 1, pp. 51–56, 2010.

[11] A. M. Neville and J. J. Brooks, Concrete Technology, PearsonEducation Asia Pte, Kuala Lumpur, Malaysia, 2008.

[12] V. Subramaniam, A. N. Ma, Y. M. Choo, and N. M. N.Sulaiman, “Environmental performance of the milling processof Malaysian palm oil using the life cycle assessment approach,”American Journal of Environmental Sciences, vol. 4, no. 4, pp.310–315, 2008.

[13] D. C. L. Teo, M. A. Mannan, and J. V. Kurian, “Flexuralbehaviour of reinforced lightweight concrete beams made withoil palm shell (OPS),” Journal of Advanced Concrete Technology,vol. 4, no. 3, pp. 459–468, 2006.

[14] D. C. Okpala, “Palm kernel shell as a lightweight aggregate inconcrete,” Building and Environment, vol. 25, no. 4, pp. 291–296,1990.

[15] F. O. Okafor, “Palm kernel shell as a lightweight aggregate forconcrete,” Cement and Concrete Research, vol. 18, no. 6, pp. 901–910, 1988.

[16] P. Shafigh, M. Z. Jumaat, and H. Mahmud, “Oil palm shell as alightweight aggregate for production high strength lightweightconcrete,”Construction and BuildingMaterials, vol. 25, no. 4, pp.1848–1853, 2011.

[17] J. Newman and P. Owens, Properties of Lightweight Concrete,Advanced Concrete Technology Set, Butterworth-Heinemann,Oxford, UK, 2003.

[18] Z. Li, Advanced Concrete Technology, John Wiley & Sons, 2011.[19] ASTM C192-90a, “Standard test method of making and curing

concrete test specimens in the laboratory,” in Annual Book ofASTM Standards, 1990.

[20] M. K. Yew, H. B. Mahmud, B. C. Ang, and M. C. Yew, “Effectsof heat treatment on oil palm shell coarse aggregates for highstrength lightweight concrete,”Materials andDesign, vol. 54, pp.702–707, 2014.

[21] M. K. Yew, I. Othman,M. C. Yew, S. H. Yeo, andH. B.Mahmud,“Strength properties of hybrid nylon-steel and polypropylene-steel fibre-reinforced high strength concrete at low volumefraction,” International Journal of Physical Sciences, vol. 6, no.33, pp. 7584–7588, 2011.

[22] N. A. Memon, S. R. Sumadi, and M. Ramli, “Performance ofhigh wokability slag-cement mortar for ferrocement,” Buildingand Environment, vol. 42, no. 7, pp. 2710–2717, 2007.

[23] A. Noushini, K. Vessalas, G. Arabian, and B. Samali, “Dryingshrinkage behaviour of fiber reinforced concrete incorporatingpolyvinyl alcohol fibers and fly ash,”Advances in Civil Engineer-ing, vol. 2014, Article ID 836173, 10 pages, 2014.

[24] C. Qian and P. Stroeven, “Fracture properties of concretereinforced with steel-polypropylene hybrid fibres,” Cement andConcrete Composites, vol. 22, no. 5, pp. 343–351, 2000.

[25] E. T. Dawood andM. Ramli, “Flowable high-strength system asrepair material,” Structural Concrete, vol. 11, no. 4, pp. 199–209,2010.

[26] G. Lu, K. Wang, and T. J. Rudolphi, “Modeling rheologicalbehavior of highly flowable mortar using concepts of particleand fluid mechanics,” Cement and Concrete Composites, vol. 30,no. 1, pp. 1–12, 2008.

[27] H. Okamura andM. Ouchi, “Self compacting concrete,” Journalof Advanced Concrete Technology, vol. 1, pp. 5–15, 2003.

[28] M. K. Yew and I. Othman, “Mechanical properties of hybridnylon-steel- and steel-fibre-reinforced high strength concreteat low fibre volume fraction,” Advanced Materials Research, vol.168–170, pp. 1704–1707, 2011.

[29] G. Campione, N. Miraglia, and M. Papia, “Mechanical proper-ties of steel fibre reinforced lightweight concrete with pumicestone or expanded clay aggregates,” Materials and Structures,vol. 34, no. 238, pp. 201–210, 2001.

[30] A. Sivakumar, “Influence of hybrid fibers on the post crackperformance of high strength concrete: part I experimentalinvestigations,” Journal of Civil Engineering Construction Tech-nology, vol. 2, no. 7, pp. 147–159, 2011.

[31] L. Domagala, “Modification of properties of structurallightweight concrete with steel fibres,” Journal of CivilEngineering and Management, vol. 17, no. 1, pp. 36–44,2011.

[32] B. Arisoy and H.-C. Wu, “Material characteristics of highperformance lightweight concrete reinforced with PVA,” Con-struction and Building Materials, vol. 22, no. 4, pp. 635–645,2008.


[33] M. K. Yew, H. Mahmud, B. C. Ang, and M. C. Yew, “Enhance-ment of mechanical properties in polypropylene twisted bun-dle fiber-reinforced oil palm shell high-strength lightweightconcrete,” in Proceedings of the 8th International Conferenceon Engineering and Technology Research, Novotel World TradeCentre, Dubai, UAE, 2014.

[34] M. A. Mannan, J. Alexander, C. Ganapathy, and D. C. L.Teo, “Quality improvement of oil palm shell (OPS) as coarseaggregate in lightweight concrete,” Building and Environment,vol. 41, no. 9, pp. 1239–1242, 2006.

[35] U. J. Alengaram, H.Mahmud, andM. Z. Jumaat, “Enhancementand prediction of modulus of elasticity of palm kernel shellconcrete,” Materials and Design, vol. 32, no. 4, pp. 2143–2148,2011.

[36] J. Newman and B. S. Choo, Advanced Concrete Technology:Testing and Quality, Butterworth-Heinemann, Oxford, UK,2003.

[37] S. Chandra and L. Berntsson, Lightweight Aggregate Concrete:Science, Technology, and Applications, Noyes/William A, NewYork, NY, USA, 2002.

[38] I. B. Topcu and T. Uygunoglu, “Effect of aggregate type onproperties of hardened self-consolidating lightweight concrete(SCLC),” Construction and Building Materials, vol. 24, no. 7, pp.1286–1295, 2010.

[39] R. V. Balendran, F. P. Zhou, A. Nadeem, and A. Y. T. Leung,“Influence of steel fibres on strength and ductility of normal andlightweight high strength concrete,” Building and Environment,vol. 37, no. 12, pp. 1361–1367, 2002.

[40] P. Shafigh, H. B. Mahmud, and M. Z. Jumaat, “Oil palm shelllightweight concrete as a ductilematerial,”Materials andDesign,vol. 36, pp. 650–654, 2012.

[41] A. Turatsinze and M. Garros, “On the modulus of elasticityand strain capacity of self-compacting concrete incorporatingrubber aggregates,” Resources, Conservation and Recycling, vol.52, no. 10, pp. 1209–1215, 2008.

[42] H. Akbar, Design of Reinforced Concrete Structures, vol. 1, Basictopics, Simay Danesh, Tehran, Iran, 2008.

[43] Z. Li, Advanced Concrete Technology, John Wiley & Sons, NewYork, NY, USA, 2011.

[44] P. Balaguru and A. Foden, “Properties of fiber reinforcedstructural lightweight concrete,” ACI Structural Journal, vol. 93,no. 1, pp. 62–78, 1996.

[45] P. Balaguru and M. G. Dipsia, “Properties of fiber reinforcedhigh-strength semilightweight concrete,”ACIMaterials Journal,vol. 90, no. 5, pp. 399–405, 1993.

[46] U. J. Alengaram, M. Z. Jumaat, and H. Mahmud, “Influenceof sand content and silica fume on mechanical properties ofpalm kernel shell concrete,” in Proceedings of the InternationalConference on Construction and Building Technology (ICCBT’08), pp. 251–262, 2008.

[47] M. A. Mannan and C. Ganapathy, “Engineering properties ofconcrete with oil palm shell as coarse aggregate,” Constructionand Building Materials, vol. 16, no. 1, pp. 29–34, 2002.

[48] U. J. Alengaram, M. Z. Jumaat, and H. Mahmud, “Ductilitybehaviour of reinforced palm kernel shell concrete beams,”European Journal of Scientific Research, vol. 23, no. 3, pp. 406–420, 2008.

[49] T. Y. Lo, H. Z. Cui, and Z. G. Li, “Influence of aggregate pre-wetting and fly ash on mechanical properties of lightweightconcrete,”Waste Management, vol. 24, no. 4, pp. 333–338, 2004.

[50] C. Shi, Y. Wu, and M. Riefler, “Properties of fiber-reinforcedlightweight concrete,”ACI Special Publication, vol. 226, pp. 123–134, 2005.

[51] CEB/FIPManual of Design and Technology, Lightweight Aggre-gate Concrete, 1997.

[52] R. N. Swamy and G. H. Lambert, “Mix design and propertiesof concrete made from PFA coarse aggregates and sand,”International Journal of Cement Composites and LightweightConcrete, vol. 5, no. 4, pp. 263–275, 1983.

[53] P. K. Mehta and P. J. M. Monteiro, Concrete: Microstructure,Properties, and Materials, McGraw-Hill, New York, NY, USA,3rd edition, 2006.

[54] H. Mazaheripour, S. Ghanbarpour, S. H. Mirmoradi, andI. Hosseinpour, “The effect of polypropylene fibers on theproperties of fresh and hardened lightweight self-compactingconcrete,”Construction and BuildingMaterials, vol. 25, no. 1, pp.351–358, 2011.

Submit your manuscripts athttp://www.hindawi.com

ScientificaHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation http://www.hindawi.com Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation http://www.hindawi.com Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttp://www.hindawi.com Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials

research article effects of low volume fraction of...

Documents